Bacteria are utilized in a wide range of commercial applications. For example, lactic acid bacteria cultures are used to produce cheese, yogurt, and other dairy products. Lactobacillus acidophilus, Bifidobacteria, E. coli and other types of bacteria are extensively used as probiotics. Live attenuated bacteria are extensively used to vaccinate different domestic animals and humans. Genetically altered bacteria are widely used as expression hosts for a variety of proteins and products.
Bacterial viruses (bacteriophages) may be used as an alternative to anti-bacterial antibiotics (phage therapy) and as vectors for gene delivery (viral and non-viral vectors) [1-3], which uses require that the bacterial viruses are delivered to a desired destination in an intact and viable form.
Bacteria can be preserved in a dry form, e.g. by lyophilization, or in a wet form as concentrated cells. Wet storage preserves bacterial cells only for a relatively short period. On the other hand, bacteriophages can sometimes be preserved in liquid form for relatively long periods, depending on the type of virus preserved.
Dry form storage has the advantages of reduced weight and requires reduced space for storage. Room temperature storage of dried materials is moreover cost effective when compared to low temperature storage options and the concomitant cost. However, lyophilization leads to loss of viability, loss of virulence and occurrence of mutations with many bacterial strains, and the vial in which the bacteria are stored cannot be resealed after opening, such that any remaining material must be discarded. Lyophilization is not suitable for phage therapy.
The preservation and storage of biologically active materials in dry form, while maintaining its activity, is important for many applications in the food and microbiological industries, agriculture, medical and research purposes.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method of preserving bacteria and non-filamentous viruses in viable form.